Crucible furnace



1941- R. D. YORK ET'AL 4,

. CRUCiBLE FURNACE Fil'ed May 9, 1939 I5 Sheets-Sheet l IIIIII 'l 2 1 tom 5? 3M PAY/"0N0 D. YORK I C L /MMMEE Gum ' Dec. 2, 1941. R. D. YORK ETAL 2,264,926

CRUCIBLE FURNACE Filed May 9} 1939 3 Sheets-Sheet 2 L A I L."

Patented Dec. 2, 1941 2,264,926 CRUCIBLE FURNACE'V as trustee Application May 9, 1939, Serial-No. 272,658:

21 Claims.

This invention relates to crucible furnaces, and method of making the same.

Coke-fired furnaces, of. course,-are very old, but with the development of other types of furnaces, the use of coke furnaces has been reduced practically to the point of abandonment due to their numerous disadvantages. For example, .in prior types of coke furnaces it was extremely difficult to properly support a crucible either in stationary or tilting. type furnaces. Moreover, the supporting. blocks for the crucibles almost invariably would be lifted out of the furnace with the crucible upon removal of the latter. Prior coke furnaces have been disadvantageous for other reasons, as is well known.

An important object of the present invention is to provide a coke-fired crucible furnace, which overcomes all of the disadvantages of prior coke furnaces, while retaining the advantages thereof such, for example, as extreme economyin manu-z n.

facture and use.

More specifically an important object of the invention is to provide a novel structure wherein the block for supporting the crucible is anchored with respect to the grate and accordingly is not withdrawn from the furnace with the crucible.

A further object is to provide a furnace wherein the crucible supporting block rests upon a weight-supporting structure wholly independent of the grate, thus preventing th grate from being subjected to the load of the crucible and the contents thereof.

A further object is to provide a novel structure for more efiiciently supporting the grate, andto utilize the crucible supporting block for this purpose.

A further object is to provide a novel structure of the character referred to wherein the grate,-

the crucible supporting block and the supporting structure for such elements all may be removed from the bottom of the furnace, thus greatly facilitating replacement of the parts.

A further object is to provide a novel supporting block structure of such character thatthe portions of the block which are first normally destroyed in operation can be readily replaced without the necessity of replacingthe entire block, thus effecting a material saving in replacement costs.

A further object is to provide a furnace struc-' ture wherein metal may be readily removed from the base structure in the event of the breakage of the crucible under which conditions molten metal in the crucible flows downwardly into the base'structure.

A further objectis toprovide a novelstructure of a crucible from a stationary furnace, or to per mit the pouring of metal from a tilting furnace.

A'further object is to provide a novel method of making cruciblesupporting-blocks in a plurality of parts whereby the parts. will'not adhere to each other in'theuse-of the-furnace, thus-permittinga portion. of the block to berenewed without having torepla-ce the entire block.

Other objects and advantages of theinvention will become apparent during the :courseof the following descriptionr In the. drawings we have-shown two embodiments of the invention. In this showing? Figure 1 is a side-elevation of a stationary type furnace,

Figure 2 is a .plan. viewuofuthel same showing the cover swung to. inoperative position,

Figure 3 is. acentraLvertical. sectional view. through the. furnace,-. parts being. shown' in elevation, I

Figure 4 is.a detail perspective-view oflthe crucible supporting block showing ithe'element thereof separated,

Figure 5 is a central vertical sectional: view through a furnace'of the tilting type, and,

Figure 6 is a detail perspective viewof the'cru-. cible supporting block'for the tilting type furnace, the parts being shown separated.

Referringto Figures 1 to 3 inclusive, the numeral l0 designates the furnace as a-whole having the wall structure thereof made up of insulation H of any suitable material and an. inner fire brick structure I2, the spac within the fire brick forming the fire pot'of the. furnace. As previously indicated the furnace is of the cokeburning type, the fuel being supported on an annular grate 83,. the diameter of which .is preferably slightly smaller than the space in the portion of the fire box within which it is arranged to permit the grate to be removed from the bottom of the furnace in a manner to be described. The furnace walls rest upon a base structure M having a lower preferably steel wall l5, the base and side wall'structure being preferably surrounded by a steel jacket 16 which'extends substantially below the wall H: for apurpose to be described.

A load supporting elementindicated as a whole by the numeral l! is arranged beneath the grate, as shown in Figure 3. This element comprises an annular cylindrical flange l8 arranged within the bottom of the base structure l4 and having its upper edge engaging the peripheral portion of the grate to support the latter. The load supporting element further comprises a horizontal flange l9 bolted as at to the bottom plate |5 whereby the load supporting element is supported with respect to the furnace structure. The element also includes a downwardly converging conical portion 2|. The annular portions of the element H are connected by vertical integral cross members 22 and an upper platform 23 is formed integral with the cross members 22 and has its upper surface on a common horizontal plane with the upper edge of the flange l8. It will be apparent that the grate I3 is formed circular in shape and is provided with an upwardly diverging conical axial opening 24 the bottom of which is of smaller diameter than the platform 23 whereby the inner peripheral portion of the grate is supported by such platform.

A crucible 25 is arranged within the furnace and is adapted to be supported by a block indicated as a whole by the numeral 26. This block is formed in two parts as shown in Figures 3 and 4, one part 21 being the permanent part of the block structure and the part 28 being the replaceable part. The permanent block element 21 comprises an upper frustro-conical portion 25 and a lower base portion of circular crosssection, the peripheral surface of the base portion 30 corresponding in taper to and being arranged within the opening 24 and forming a snug fit therewith whereby the base portion 3|], which rests on the platform 23, assists both in positioning and supporting the grate.

The replaceable block portion 28 is provided with an opening 3| tapered to correspond with the taper of the block portion 29 but of somewhat greater diameter so as to normally provide an annular space therebetween. For a purpose which will be referred to in detail, the outer surface of the block portion 29 and the upper surface of the block portion 30 are covered with a layer of material such as paper, as indicated by the numeral 32, prior to assembling the elements of the supporting block, and the remaining space within the block element 28 is filled with a suitable cement 33. The crucible and both of the block elements are preferably formed of graphite and clay in accordance with common practice, the use of these materials being advisable but frequently resulting in the substantial adhering of the bottom of the crucible to the supporting block adjacent the outer portion thereof. The present construction overcomes the disadvantages of such adhersion between the crucible and the block as will be referred to later.

A horizontal plate 34 is arranged parallel to and spaced beneath the bottom plate l5 and the space between these plates is surrounded by the furnace jacket IE to form an annular space 35. At one side of such space, the jacket I6 is provided with an air inlet opening 36 and a blower 31 is bolted or otherwise secured to the jacket |6 with its outlet 38 communicating with the opening 36. A baffle 39, preferably of V-shape is arranged inwardly of the opening 36 to spread the incoming air from the blower around the annular space to secure an even distribution of the air for delivery to the grate. The conical bottom 2| of the supporting element l1 assists in distributing the air uniformly around the grate,

iii)

it being necessary for the air to pass downwardly around the conical portion 2| and upwardly therethrough to reach the grate.

A conical ash pit 40 is arranged beneath the furnace and is provided with an outstanding annular flange 4| secured in position by means of bolts 42. These bolts preferably extend through the walls l5 and 34 and serve to support the latter in position, the bolts 42 being surrounded by spacing sleeves 43 to fix the distance between the plates l5 and 34. The bottom of the ash pit is closed by a door 44 pivoted to the ash pit as at 45 and held in snug engagement with the ash pit by a spring arm 46. Any suitable form of handle may have its inner end 41 connected to the door 44 diametrically opposite the pivot pin 45 whereby the door may be swung to open position to dump the ashes from the pit. The door 44 may be arranged a suitable distance above the floor level 48 and on the floor is arranged a suitable base structure 49 carrying legs 50 by means of which the entire furnace is supported.

A cover 5| is arranged over the furnace and normally occupies the closed position shown in Figure 3. The cover is frustro-conical in shape with an annular bottom portion resting upon the furnace and the upper portion of the cover is provided with a plurality of openings 52 for the escape of at least a portion of the products of combustion. The open top of the cover 5| is provided with a plurality of inwardly extending lugs 53 defining a space to receive and position a preheating hopper 54 having radially projecting lugs 55 of a width sufiicient to overhang and be supported by the body of the cover 5| radially outwardly of the lugs 53. Within its tapered portion, the cover may be provided with suitable lugs 56 to assist in positioning the hopper 54 and preventing any swinging movement thereof out of its axial position with respect to the crucible. The lugs 55 are preferably equal in number to the lugs 53 and may either overhang such lugs or may be arranged therebetween to substantially seal the top of the cover, as may be desired. The upper end of the cover 5| may be provided with a suitable clamping band 51 to act as a bracing means for the cover.

Novel means for elevating and swinging the cover 5| are employed. A bearing structure indicated as a whole by the numeral 58 is bolted or otherwise secured against the jacket l6 near the top thereof and includes spaced bearings 59 and 60 receiving a shaft 6|. This shaft does not move vertically in the bearings 59 and 60 but is free to swing therein, the lower bearing 66 having a closed bottom end provided with an upstanding substantially hemispherical element 52 acting as a thrust bearing to support the shaft 6| and the load of the elements carried thereby under certain conditions to be described.

A casting indicated as a whole by the numeral 63 includes a cylindrical portion 64 surrounding the shaft BI and provided respectively adjacent its upper and lower ends with rollers 55 and 56 arranged at diametrically opposite points with respect to the shaft 6| to carry the stresses to which the latter is subjected in a manner to be described. The bottom portion of the cover 5| has its peripheral surface engaged by a plurality of arcuate band sections 61 the ends of which are turned outwardly and connected by bolts 68 which extend tangentially of the cover and engage within a groove 69 formed therein. The band sections 61 also may be provided with inwardly extending arcuate portions engaging within suchgroove as shown in Figure 3.. The band sections 61 and boltsBB comprise a clamping structure surrounding the bottom of the cover 51 and two angle braces 69 are connectedbetween such structure. and a .pairuof. ears formed integral with the. casting 63 as. shown-.in Figure 2. These braces serve to effectively con-1 nect the load of the coverto the castingiiii. The lower end ofsuch casting is provided with an extended portion ll receiving a shahkfli carriedbyone of the bandsections $1 to also anchor he cover 5| with respect to. the bottom of the casting .63. This casting has angularly arran ed e por ns 13 and I inclined in the. direction shown in F ure 3 to. distribute the load trans: mitted by the braces 69 throughout the casting B3.

A pair of links 15 have their upper ends pivotally connected asat 16 to the web I3 and extending on opposite sides of a projection 'Il formed integral with the casting 63 asshown in Figur 3., A lever I8, having a handle I9 at its upper end, is pivotally connected as at 8i] to arms BI formed integral with a block 82 fixed to the shaft BI. The lever 18 is provided witha short arm 83 to which the lower ends of the link '75. are pivoted as at 84, The lever normally occupies the position shown in Figure 3 with its long arm, engaging the projection TI to limit inward movement of the lever. A projection 85,

formed integral with the lever, is engageable in a recess 86 formed in th block 82 when the handle I9 is swung downwardly to a horizontal position,- this construction being employed to. limit downward swinging of the handle I0, and to connect the lever to the block 82; whereby the lever is assisted in turning the shaft 6| on its axis upon swinging movement of the handle lever in a horizontal plane.

The ash pit preferably is of a capacity at least equal to the capacity of the crucible 25 whereby it is adapted to receive all of the molten metal from the crucible in the event the crucible breaks and-all of the metal flows therefrom. The conical shape of the ash pit permits it to be removed to permit the dumping of the metal therefrom under the conditions stated. It is preferred however,- that the ash pit be provided with a plurality of weeper holes 87, arranged at different levels, and each covered with a relatively thin lead or similar plate 88 having a relatively low melting point to be melted by molten metal which may collect in the ash pit under the conditions referred to.

The invention is shown in Figures 5 and 6 in connection with a tilting type furnace in which most of th parts are identical with the parts previously described. Such parts need not be referred to in detail, therefore, and they have been indicated by the same reference numerals. The particular means for supporting the furnace for tilting movement is of no particular importance and may be of any desired type and accordingly th furnace has been generally indicated as being capable of support for tilting movement by means of trunnions 89. Since the furnace in Figure 5 is of the tilting type, it employs acrucible having a pouring lip 9| extending radially with respect to the furnace and arranged in a recess 02 formed in the upper end thereof. The furnace itself is provided with a pouring spout 93 through which the molten metal may flow from the pouring lip 9 I.

The tilting type furnace preferably employs a crucible supporting block of somewhat different construction from that previously describedasfshown in Figures 5 and 6. This sunporting block is indicated as a whole by the numeral. 94 and comprises upper and lower 'ele-. ments 55 and 96. the lower of which has its bottom portion formed frustro-conical as at 01 to fit within the conical opening 24 of the grate. The upper element 95 is provided with a preferably, axial upwardly extending lug 98 engageable in a similarly shaped recess 99. formed in the bottom: of the crucible. The lower element 96 is provided with a similar lug I00 receivablein a corresponding opening IiiI formed in the bottom of the element;95, a layer of paper I02: being arrangedbetween and coextensive with the adiaccntjfaces of the block elements 95 and 56:

It will be apparent that the crucible of a tilting furnace possibly may break while the .fur-. nace is in a pouring position. Accordingly, the conical flange 2| of the supporting element I1 is provided with a weeper hole I03jin the side thereof corresponding. to the. pouring side .of theyfurnaoe and normally covered by a thin leador similar sheet I04 similar to thesheets 88 previously described. The furnace jacket lfi is providedv with a similarly arranged opening :05, normally covered'by a lead or similar plate I06.. Any breakage of the crucible whilethe furnace is in pouring position accordingly will result in at least some of the metal melting the plates I04 .and I05 and pouring fromthe furnac through the openings I53 and E55.

Theoperation of the form of the invention shown inFigures 1 to 4, inclusive, is as follows:

The furnace is operated generally in accordance with'conventionai practice in the operation of a coke-fired furnace. The metal is melted in the crucible by the surrounding fire and in loading the crucible, the metal extends upwardly into .the preheating hopper 55. The products of combustion flowing upwardly around the hopper preheats the metal therein and thus prepares it for movement downwardly into the crucible-as the metal melts therein. Some of the products of combustion will flow through the openings-52 and part will normally flow between the lugs 53-, thus effectively heating the metal in the hopper. If desired, the hopper 54 may be turned to cause the lugs 55 to close the spaces between the lugs 53. These lugs, and the lugs 56, serve to properly position. the hopper 54 in axial alignment with the crucible, the hopper being prevented from swinging laterally. at its lower end.

The blower 31 may be provided with a very low-powered drivingmotor to provide a forced draft to the fuel in the fire box. The size of such motor as well as its power and the cost of operating it is only a fraction of the cost involved in connection with oil-burning crucible furnaces and the cost of current in electric furnaces. The air being pumped into the furnace is divided by the loaffle 39 to be spread around the annular space 35 through which the air flows downwardly and radially inwardly in the space between the tapered wall 2I and the upper portion of the ash pit, and then flows upwardly within the support I1 and through. the grate I3. The structure referred to effectively and uniformly feeds air to the coke and when the proper grade of coke is employed combustion has been found to be so complete as to leave a very small residue of ash for collection from the ash pit 45.

In theevent of breakage of the crucible, the molten metal will flow downwardly through the grate and into the ash pit and will melt one or more of the lead plates 88. to flow from the ash pit. However, the ash pit tapers to increase in size toward its upper end and is of a capacity equal to the capacity of the crucible so that in the event of the failure of the molten metal to be discharged through the Weeper openings, the ash pit will contain all of the molten metal thus preventing it from setting around and in engagement with any portion of the support. H. The removal of.the nuts from the lower ends of the bolts 42 permits the removal of the ash pit, whereupon it may be inverted to drop the metal therefrom. In this connection attention is invited to the fact that all portions of each opening 81 diverge upwardly from the vertical, and thus any metal which has set in the openings 81 will readily move out of engagement therewith upon the inversion of the ash pit in the manner stated.

It will be noted that the grate i3 is not subjected to any bending stresses under the influence of loads thereabove. The crucible is supported by the block structure 26, the member 21 of which is directly supported upon the platform 23. A portion of the block element 28 will be supported on the inner portion of the grate but H such portion of the grate is directly supported by the platform 23 and accordingly it will be apparent that the grate is called upon to support solely the weight of the fuel.

When it is desired to remove the crucible from the furnace to pour the metal therefrom, the operator will first swing the handle lever IS in a clockwise direction as viewed in Figure 3 until it reaches a horizontal position whereupon the handle is swung in a horizontal plane to swing the cover 5| to open position. The block 82 is fixed to the shaft H and upon downward swinging movement of the lever 18 the pivot pin 84 elevates the links to transmit similar movement to the casting 63, thus elevating the cover 5|. This elevation of the cover takes place to a sufficient extent to place all portions of thecover and the lower end of the hopper 54 above the horizontal plane of the upper limit of the furnace.

When the lever 18 reaches the horizontal position referred to its turning movement will be limited by engagement of the lug 85 in the recess 86. When the handle lever is then swung in a horizontal plane the engagement of the lug 85 in the recess 86 causes the block 82 to turn the shaft 6| on its axis. Moreover the links 15, engaging opposite sides of the projection 11, will impart turning movement to the casting 63. Thus it will be apparent that the shaft BI and casting 63 turn as a unit to swing the cover to its open position. The operations referred to obviously may be reversed to close the cover for the next operation.

The mechanism referred to forms a simple and efficient cover opening and swinging mechanism. The rollers 65 and 66 reduce the friction of lateral loads transmitted to the shaft 6| to permit the cover 5| to be readily elevated prior to being swung to open position. The webs l3 and 14 effectively distribute loads throughout the length of the casting 64 as will be apparent.

When the crucible is lifted from the furnace for the purpose of pouring the metal therefrom, the crucible tends to adhere to the supporting block as will be obvious. In previous constructions this has caused substantial difficulty. In the present construction, however, the tapering of the adjacent portions of the block elements 21 and 28 between which the cement 33 is arranged effectively prevents upward movement of the outer block element 28, while the inner block element 21 will be prevented from moving upwardly by engagement of its lower portion in the tapered opening 24 of the grate.

The operation of the form of the invention shown in Figures 5 and 6 is substantially identical with the form previously described and need not be referred to in detail. The top structure is elevated and turned in the same manner as previously described, and it will be obvious that the entire furnace is tilted in accordance with conventional practice. In a tilting furnace, of course, the crucible is not removed for each pouring but remains in the furnace with the inevitable result that it very tightly adheres to its supporting block. These blocks frequently are damaged in being removed from the crucible and they are subject to burning as stated in connection with the previously described form of the invention. In the present case, the removal of the crucible, when desired, results only in the removal of the block element 95 since the paper I92 will have been reduced to powdered carbon and the lower block element 96 will be held in its position by the grate. This construction permits a damaged block element 95 to be removed independently of the block element 96 and a new element 95 may be placed in the furnace with a layer of paper I02 covering the adjacent faces of the block elements in the manner and for the purpose stated. It will be apparent that the block element 95 may be replaced for a fraction of the cost of an entire supporting block.

Inasmuch as the furnace in Figure 5 is of the tilting type, it will be apparent that upon the breaking of the crucible when the furnace is in pouring position, the lower portion of the support ll, when the furnace is in such position, may tend to trap some of the molten metal, thus making it necessary to discard the support IT. The provision of the weeper hole I03, however, overcomes this difficulty by permitting the flowing of the molten metal from the support H, the metal being discharged through the opening I as previously stated.

The numerous advantages of the present construction renders its use highly desirable over other types of crucible furnaces such as electric and oil-fired furnaces. Power costs are very greatly reduced in view of the cheapness of coke as a fuel and in view of the relatively light and cheaply operable motor employed for driving the blower 3'1. The apparatus is substantially damage-proof except as to those elements which are readily replaceable, namely, the supporting block elements 28 (Figure 3) and (Figure 5) and the lead cover plates for the various weeper openings. These parts are relatively inexpensive, and all of the remaining parts of the apparatus may be considered to be permanent in view of the characteristics of the apparatus. In actual practice, it has been found that the apparatus overcomes all serious disadvantages of prior coke-fired furnaces and has replaced a number of other types of furnaces. The use of the preheating hopper in the arrangement shown results in increasing the eificiency of the furnace by effectively preheating more metal than can be initially placed in the crucible, thus increasing the output of the furnace for each operation thereof. The efiiciency of the furnace is such that in actual practice the quality of the resulting metal usually is substantially improved.

Particular attention is invited to the novel In the tilting furnace shown in Figure it is types of crucible supporting blocks and the method of making them. In actualpractice,as pre viously' stated, the peripheral portion of the upper face of a crucible supporting block adheres very tightly to the crucible. This is particularly true in connection with tilting type furnaces wherein the metal is poured by tilting the entire furnace instead of lifting the crucible from the furnace after each operation. .In a tilting-type furnace, therefore, the crucible and its supportingblocks remain in contact through several operations.

Accordingly it is the common practice when necessary to replace a crucible to remove the crucible from the furnac with the supporting block adhering thereto and to remove the block by striking it with a sledge hammer. This is the only manner in which the block can-be removed and usually results in damaging theblock and requiring its replacement. Of course, under normal operating conditions, the blocks burn outand must be replaced and with conventional blocks it usually is the outer portion of the blocks which become damaged. Regardless of the cause of the damaging of conventional blocks of this character it will be apparent that it is necessary to replace the entire block.

The present invention provides a novel method of making the blocks thus providing a resultant block a part of which may be considered a permanent part'of 'the apparatus because of its long life. The remaining partis easily replaceable at little expense. In each form of block, the procedure in making the block comprises forming the block in two parts and so assembling the parts that they remain easily separable even after continued use in the furnace. This is accomplished by using the layer of paper 32 (Figure 3) or H12 (Figure 5) between the two parts of the block. By placing the layer of paper in position and then assembling the parts of th ..block,' the resultant block performs all of its intended functions. However, in the operation of the furnace the paper is reduced to relatively: pure carbon which cannot burn because of the absence of air, and accordingly the carbon remains in powdered form even after the furnace has been used over long periods of time.

The block structure is such, therefore, as to permit replacement only of -a part of the block instead of the entire block structure when damage occurs. In the form of the invention shown in Figure 3, the tapering of the adjacent faces of the block elements together with the use of the cement 33 serves to hold down the block element 28 thus permitting the crucible to be removed for pouring. This function of the tapering of the parts is not affected by the presence of the layer of powdered carbon to which the paper 32 is reduced, the thickness of the carbon layer being negligible. The part of the supporting block which becomes damaged will always be the upper edge of the block element 28 and when it is desirable to replace such element it'maybe broken with a sledge hammer, whereupon a new layer of paper will be applied, the block element 28 placed in position and cement poured as shown in Figure 3. In this connection attention is invited to the fact that the diameter of the lower end of the tapered opening of the block element 18 is slightly larger than the diameter of the upper end of the tapered'block portion 29, and accordingly a new block element 28 readily may be placed in position by being slipped-down over the block portion 29.

not necessary to provide any hold-down means for the supporting block since the entire furnace is tilted. If it becomes necessary to replace the block element-95, the crucible may be removed with the element adhering .to it, and this'element may be removed, whereupon anew element 95 may be placed in position with a paper layer Hi2 arranged as shown in Figure 5. Replacement of crucible supporting blocks is frequently necessary, and the block structures referredto materially reduce the cost'of replacement, itbeingapparent that the replaceable block elements are much cheaper than an entire block structure of conventional type.

While we have disclosed the preferred practice of the method and thepreferred embodiment of the apparatus, it is to be understood that the details of procedure of the method and the shape, size-and arrangement of parts of the apparatus may be variously modified without departing from the spirit of the-invention or the scope of the subjoined claims.

We claim:

1. In a crucible furnace, agrate, a crucible supporting block, and common means engaging and supporting both said grate and said block, said grate and said block having inter-engaging portions preventing upward movement of. said blockwith respect to said grate.

2. In a crucible furnace,.a furnace body, a circular grate, a crucible supporting block having a portion extending through the center of said grate, and a support carried by said furnace body and forming the sole support for said block, said gratev resting on said support to be supported thereby, said grateand the portion ofsaid block extending therethrough having inter-engaging faces preventing upward movementof said block with respect to said grate. I

3. In a crucible furnace, a furnace body having an opening therethrough, a support arranged adiacent the bottom of-said openingand carried by said furnace body, said support having a flange portion extendinginto said opening and having a platform centrally thereof spaced from said flange, a crucible supporting block supported-by said platform, and a circular grate-surrounding the bottom portion of said'block and having a portion resting on said fiange to be supported thereby, said grate and the portion ofsaid block surrounded thereby having inter-engaging portions'preventing upward movement of said'block with respect to said grate.

4. In a crucible furnace, a furnace body having an opening therethrough, a support arrangedadjacent the bottom of said opening *and carried by said furnace body, said support having afiange portion extending into said opening and having a p'latform' centrally thereof spaced from said flange, a crucible supporting block supported by said-platform, a. grate arranged in said-opening and engaging saidflange to be atleast partly supported thereby, a wall arranged to define With said furnace body an air chamber communicating with the interior of said support, said wallhaving an opening of such shape and size as to permit downward niovement of said support therethrough, a closure for said last named opening, and means for supplying air to said air chamber.

5. Ina crucible furnace, a furnace body having anopening therethrough, a support arranged adjacent the bottom of said opening and carried by said furnace body, said support having a flange portion extending into said opening and having a platform centrally thereof spaced from said flange, a crucible supporting block supported by said platform, a grate arranged in said opening and engaging said flange to be at least partly supported thereby, a wall arranged to define with said furnace body an air chamber communicating with the interior of said support and provided with a bottom opening, and an ash pit tapered to increase in size toward its upper end and arranged to form a closure for said last named opening, said ash pit having a weeper opening therethrough constructed and arranged to permit direct vertical movement of any material therein, and a plate normally covering said weeper opening and formed of a material having a relatively low melting point.

6. In a crucible furnace, a furnace body having an opening therethrough, a support arranged adjacent the bottom of said opening and carried by said furnace body, said support having a flange portion extending into said opening and having a platform centrally thereof spaced from said flange, a crucible supporting block supported by said platform, a grate arranged in said Opening and engaging said flange to be at least partly supported thereby, a wall arranged to define with said furnace body an air chamber communicating with the interior of said support and provided with a bottom opening of such shape and size as to permit downward movement of said support therethrough, and an ash pit forming a closure for said last named opening, said ash pit being tapered to increase in size toward its upper end.

'7. A crucible supporting block structure comprising a pair of approximately fitting elements, and a separating layer between said elements, said layer being formed of a material readily reducible to substantially carbonaceous form under the influence of heat, said structure being engageable with a crucible thereabove to provide a support therefor and having a continuous upper crucible-supporting surface.

8. A crucible supporting block structure comprising a pair of approximately fitting elements arranged in vertical axial alignment, said elements having adjacent horizontal faces, and one element having a portion projecting vertically into and surrounded by a portion of the other element, and a layer of material arranged between said horizontal faces and between said portions of the respective elements and formed of a material readily reducible to substantially carbonaceous form under the influence of heat, said structure being engageable with a crucible thereabove to provide a support therefor.

9. A crucible supporting block structure comprising a pair of block elements one of which is provided with an upwardly extending portion and the other of which surrounds such portion, and a separating layer between said second named element and the upwardly projecting portion of said first named element, said separating layer being formed of a material readily reducible to substantially carbonaceous form under the influence of heat.

10. A crucible supporting block structure comprising a pair of block elements one of which is provided with an upwardly extending portion and the other of which surrounds such portion,

the adjacent faces of said second named element and the upwardly projecting portion of said first named element being tapered to increase in size toward the top of the block structure, a layer of cement on one of said adjacent faces, and a sep- Cit arating layer between said cement and the other of said adjacent faces, said separating layer being formed of a material readily reducible to substantially carbonaceous form under the influence of heat. 1

11. A crucible supporting block structure comprising a pair of block elements arranged one above the other, the lower block element having a projection on its upper face and the upper block element having a recess receiving said projection, and a separating layer between the ad- J'acent faces of said block elements and between the adjacent faces of said projection and said recess, said separating layer being formed of a material readily reducible to substantially carbonaceous form under the influence of heat.

12. A crucible-supporting block assembly comprising a crucible having a recess in the bottom thereof, a block element having a projection engageable in said recess, said block element having a recess in its lower face, a second block element having a projection on its upper face extending into the recess in said first named block element, and a separating layer between said block elements formed of a material readily reducible to substantially carbonaceous form under the influence of heat.

13. In a crucible furnace, a furnace body having a fire pot therein and having means for supporting a crucible therein, a cover for said furnace body tapered to decrease in size toward its upper end, said cover having an axial opening in its top and being provided with lugs surrounding said opening, and a preheating hopper arranged in said opening and positioned therein by said lugs whereby products of combustion are adapted to flow between said lugs, said hopper having lugs at its upper end overhanging said cover to be supported thereby.

14. In a crucible furnace, a furnace body having a fire pot therein and having means for supporting a crucible therein, a cover for said furnace body tapered to decrease in size toward its upper end, said cover having an axial opening in its top and being provided with lugs surrounding said opening, and a preheating hopper arranged in said opening and positioned therein by said lugs whereby products of combustion are adapted to flow between said lugs, said hopper having lugs at its upper end overhanging said cover to be supported thereby, said cover having openings in the walls thereof for the passage therethrough of part of the products of combustion, and having lugs engaging said hopper at points spaced from the top thereof to prevent lateral swinging movement of the lower end of said hopper.

15. In a crucible furnace, a furnace body, a grate therein, and a crucible supporting block structure arranged above said grate and engage able with a crucible to support it in said furnace body, said block structure comprising a pair of approximately fitting elements, and a separating layer between said elements formed of a material readily reducible to substantially carbonaceous form under the influence of heat.

16. In a crucible furnace, a furnace body, a grate therein, and a crucible supporting block structure arranged above said grate, said block structure comprising a pair of block elements one of which is provided with an upwardly extending portion and the other of which is circular and has at least a portion thereof surrounding said upwardly extending portion, and a separating layer between the adjacent portions of said elements formed of a material readily reducible to substantially carbonaceous form under the influence of heat.

17. In a crucible furnace, a furnace body, a grate therein, and a crucible supporting block structure arranged above said grate, said block structure comprising a pair of elements one of which has a horizontal base portion and an up- Wardly projecting central portion, the other of said elements being ring-like and surrounding the upwardly projecting portion of said first named element and having its lower face parallel to the upper face of the base portion of said first named element, and a separating layer between the adjacent portions of said elements formed of a material readily reducible to substantially carbonaceous form under the influence of heat.

18. In a crucible furnace, a furnace body, a grate therein, and a crucible supporting block structure arranged above said grate, said block structure comprising a pair of block elements arranged one above the other, the lower block element having a projection on its upper face and the upper block element having a recess in its lower face of a shape and size to loosely receive said projection, and a separating layer between the adjacent portions of said block elements formed of a material readily reducible to substantially carbonaceous form under the in fluence of heat.

19. In a crucible furnace, a furnace body having a vertical opening therethrough, a support arranged at the bottom of the furnace body, said support having an outstanding flange beneath and secured to the furnace and an upstanding flange slidable within the lower end of the furnace, a platform carried by said support centrally thereof, said platform having its upper face substantially flush with the upper edge of said upstanding flange, a circular grate having its inher and outer edges resting upon and supported by said platfrom and the upper edge of said upstanding flange, and a crucible supporting block structure having a bottom portion projecting through said grate and supported on the upper face of said platform.

20. A crucible structure constructed in accordance with claim 19 wherein said bottom portion of said block structure and the inner peripheral face of said grate engage each other and are tapered to decrease in size upwardly.

21. A crucible furnace constructed in accordance with claim 19 having a wall arranged to define with said furnace body an air chamber communicating with said support between said platform and said upstanding flange, said wall having an opening of such shape and size as to permit downward movement of said support therethrough, and an ash pit forming a closure for the opening in said wall.

RAYMOND D. YORK. CHARLES M. WALKER. 

